1. Text of coupon state out you should use in-game browser for coupon.
2. Official in game browser is arc
3. Checking all arc option of browser shows, no possiblity for using this coupon.
4. Checking Lottery NPC in Arch, no options to choose
5. Checking patch notes, no information about this functionality

--> I think this functionality was not planned and only partly activated now.
Official statement would be nice.

P.S.: Click on "buy gold" helps people without any plan (e. g. if they installed already arc or they even forgot shortcut for it) to navigate fast to this browser.